ranbo'u lujvo

b1=r=1 is a/the cartilage/gristle [body-part], performing function b2 in body of b3.

x2 is likely an abstract: may be structure/support for some body part, but others as well. See also: bongu.

In notes:

bongu
x1 is a/the bone/ivory [body-part], performing function x2 in body of x3; [metaphor: calcium].